July 15, 2013
01:00 PM (EDT)

News Release Number: STScI-2013-30

Hubble Finds New Neptune Moon

July 15, 2013: In the summer of 1989, a robotic emissary from Earth visited the
farthest major planet from the Sun, Neptune. Like any good tourist, NASA's
Voyager 2 spacecraft snapped a lot of pictures during the brief flyby. The
prolific probe discovered several moons orbiting close to the blue-green
planet. But one moon, no bigger than a metropolitan city and nearly
coal-black, escaped detection because it was too faint to be seen. Until now.

While analyzing Neptune photos taken by the Hubble Space Telescope,
astronomer Mark Showalter of the SETI Institute noticed an extra white dot
about 65,400 miles from Neptune, located between the orbits of the moons
Larissa and Proteus. Hubble's extraordinary sensitivity and sharpness caught
an object that is roughly one hundred million times fainter than the faintest
star that can be seen with the naked eye. Thankfully, Showalter also had 150
archival Neptune photographs taken by Hubble from 2004 to 2009. The same
white dot appeared over and over again. This allowed him to plot a circular
orbit for the moon, designated S/2004 N 1, which completes one revolution
around Neptune every 23 hours. His discovery raises the number of known moons
orbiting Neptune to 14.